Genlist

../_images/genlist-preview.png

Widget description

This widget aims to have more expansive list than the simple list in Elementary that could have more flexible items and allow many more entries while still being fast and low on memory usage. At the same time it was also made to be able to do tree structures. But the price to pay is more complexity when it comes to usage. If all you want is a simple list (not much items) with icons and a single text, use the normal List object.

Genlist has a fairly large API, mostly because it’s relatively complex, trying to be both expansive, powerful and efficient. First we will begin an overview on the theory behind genlist.

Genlist item classes - creating items

In order to have the ability to add and delete items on the fly, genlist implements the item class (callback) system where the application provides a structure with information about that type of item (genlist may contain multiple different items with different classes, states and styles). Genlist will call the functions in this class (methods) when an item is “realized” (i.e., created dynamically, while the user is scrolling the grid). All objects will simply be deleted when no longer needed with efl.evas.Object.delete(). GenlistItemClass contains the following members:

  • item_style - This is a constant string and define the name of the default item style. It must be provided.

  • decorate_item_style - This is a constant string and define the name of the style to be used in the “decorate” mode. See GenlistItem.decorate_mode.

  • decorate_all_item_style - This is a constant string and define the name of the style to be used in the “decorate all” mode. See Genlist.decorate_mode.

  • text_get - This function will be called for every text part. Should return the text to display. See GenlistItemClass.text_get().

  • content_get - This function will be called for every content part. Should return an object to display, the object will be deleted by the genlist on its deletion or when the item is “unrealized”. See GenlistItemClass.content_get().

  • state_get - This function will be called for every state part. Must return True for false/off or True for true/on. Genlists will emit a signal to its theming Edje object with "elm,state,xxx,active" and "elm" as “emission” and “source” arguments, respectively, when the state is true (the default is false), where xxx is the name of the (state) part. See GenlistItemClass.state_get().

  • func.del - This is intended for use when genlist items are deleted, so any data attached to the item (e.g. its data parameter on creation) can be deleted. See GenlistItemClass.delete().

Available item styles

  • default The default style: icon, text, end icon

  • default_style The text part is a textblock and can use markups

  • double_label Two different text parts

  • icon_top_text_bottom

  • group_index

  • one_icon Only 1 icon (left) (since: 1.1)

  • end_icon Only 1 icon (at end/right) (since: 1.1)

  • no_icon No icon (since: 1.1)

  • full Only one object, elm.swallow.content, which consumes whole area of the genlist item (since: 1.7)

  • indent Has indentation to match tree group items (since: 1.19)

Structure of items

An item in a genlist can have 0 or more texts (they can be regular text or textblock Evas objects - that’s up to the style to determine), 0 or more contents (which are simply objects swallowed into the genlist item’s theming Edje object) and 0 or more boolean states, which have the behavior left to the user to define. The Edje part names for each of these properties will be looked up, in the theme file for the genlist, under the Edje (string) data items named labels, contents and states, respectively. For each of those properties, if more than one part is provided, they must have names listed separated by spaces in the data fields. For the default genlist item theme, we have one text part (elm.text), two content parts (elm.swallow.icon and elm.swallow.end) and no state parts.

Editing and Navigating

Items can be added by several calls. All of them return a GenlistItem handle that is an internal member inside the genlist. They all take a data parameter that is meant to be used for a handle to the applications internal data (eg. the struct with the original item data). The parent parameter is the parent genlist item this belongs to if it is a tree or an indexed group, and None if there is no parent. The flags can be a bitmask of ELM_GENLIST_ITEM_NONE, ELM_GENLIST_ITEM_TREE and ELM_GENLIST_ITEM_GROUP. If ELM_GENLIST_ITEM_TREE is set then this item is displayed as an item that is able to expand and have child items. If ELM_GENLIST_ITEM_GROUP is set then this item is group index item that is displayed at the top until the next group comes. The func parameter is a convenience callback that is called when the item is selected and the data parameter will be the func_data parameter, obj be the genlist object and event_info will be the genlist item.

GenlistItem.append_to() adds an item to the end of the list, or if there is a parent, to the end of all the child items of the parent. GenlistItem.prepend_to() is the same but adds to the beginning of the list or children list. GenlistItem.insert_before() inserts at item before another item and GenlistItem.insert_after() inserts after the indicated item.

The application can clear the list with Genlist.clear() which deletes all the items in the list and delete() will delete a specific item. GenlistItem.subitems_clear() will clear all items that are children of the indicated parent item.

To help inspect list items you can jump to the item at the top of the list with Genlist.first_item which will return the first item, and similarly Genlist.last_item gets the item at the end of the list. GenlistItem.next and GenlistItem.prev get the next and previous items respectively relative to the indicated item. Using these calls you can walk the entire item list/tree. Note that as a tree the items are flattened in the list, so GenlistItem.parent will let you know which item is the parent (and thus know how to skip them if wanted).

Multi-selection

If the application wants multiple items to be able to be selected, Genlist.multi_select can enable this. If the list is single-selection only (the default), then Genlist.selected_item will return the selected item, if any, or None if none is selected. If the list is multi-select then Genlist.selected_items will return a list (that is only valid as long as no items are modified (added, deleted, selected or unselected)).

Usage hints

There are also convenience functions. efl.elementary.object_item.ObjectItem.widget will return the genlist object the item belongs to. GenlistItem.show() will make the scroller scroll to show that specific item so its visible. efl.elementary.object_item.ObjectItem.data returns the data pointer set by the item creation functions.

If an item changes (state of boolean changes, text or contents change), then use GenlistItem.update() to have genlist update the item with the new state. Genlist will re-realize the item and thus call the functions in the _Elm_Genlist_Item_Class for that item.

Use GenlistItem.selected to programmatically (un)select an item or get its selected state. Similarly to expand/contract an item and get its expanded state, use GenlistItem.expanded. And again to make an item disabled (unable to be selected and appear differently) use GenlistItem.disabled to set this and get the disabled state.

In general to indicate how the genlist should expand items horizontally to fill the list area, use Genlist.mode. Valid modes are ELM_LIST_LIMIT, ELM_LIST_COMPRESS and ELM_LIST_SCROLL. The default is ELM_LIST_SCROLL. This mode means that if items are too wide to fit, the scroller will scroll horizontally. Otherwise items are expanded to fill the width of the viewport of the scroller. If it is ELM_LIST_LIMIT, items will be expanded to the viewport width if larger than the item, but genlist widget with is limited to the largest item. D not use ELM_LIST_LIMIT mode with homogeneous mode turned on. ELM_LIST_COMPRESS can be combined with a different style that uses Edje’s ellipsis feature (cutting text off like this: “tex…”).

Items will only call their selection func and callback when first becoming selected. Any further clicks will do nothing, unless you enable always select with Genlist.select_mode as ELM_OBJECT_SELECT_MODE_ALWAYS. This means even if selected, every click will make the selected callbacks be called. Genlist.select_mode as ELM_OBJECT_SELECT_MODE_NONE will turn off the ability to select items entirely and they will neither appear selected nor call selected callback functions.

Remember that you can create new styles and add your own theme augmentation per application with efl.elementary.theme.Theme.extension_add(). If you absolutely must have a specific style that overrides any theme the user or system sets up you can use efl.elementary.theme.Theme.overlay_add() to add such a file.

Scrollable Interface

This widget supports the scrollable interface.

If you wish to control the scrolling behaviour using these functions, inherit both the widget class and the Scrollable class using multiple inheritance, for example:

class ScrollableGenlist(Genlist, Scrollable):
    def __init__(self, canvas, *args, **kwargs):
        Genlist.__init__(self, canvas)

Implementation

Evas tracks every object you create. Every time it processes an event (mouse move, down, up etc.) it needs to walk through objects and find out what event that affects. Even worse every time it renders display updates, in order to just calculate what to re-draw, it needs to walk through many many many objects. Thus, the more objects you keep active, the more overhead Evas has in just doing its work. It is advisable to keep your active objects to the minimum working set you need. Also remember that object creation and deletion carries an overhead, so there is a middle-ground, which is not easily determined. But don’t keep massive lists of objects you can’t see or use. Genlist does this with list objects. It creates and destroys them dynamically as you scroll around. It groups them into blocks so it can determine the visibility etc. of a whole block at once as opposed to having to walk the whole list. This 2-level list allows for very large numbers of items to be in the list (tests have used up to 2,000,000 items). Also genlist employs a queue for adding items. As items may be different sizes, every item added needs to be calculated as to its size and thus this presents a lot of overhead on populating the list, this genlist employs a queue. Any item added is queued and spooled off over time, actually appearing some time later, so if your list has many members you may find it takes a while for them to all appear, with your process consuming a lot of CPU while it is busy spooling.

Genlist also implements a tree structure, but it does so with callbacks to the application, with the application filling in tree structures when requested (allowing for efficient building of a very deep tree that could even be used for file-management). See the above smart signal callbacks for details.

Emitted signals

  • activated - The user has double-clicked or pressed (enter|return|spacebar) on an item. The event_info parameter is the item that was activated.

  • clicked,double - The user has double-clicked an item. The event_info parameter is the item that was double-clicked.

  • clicked,right - The user has right-clicked an item. The event_info parameter is the item that was right-clicked. (since: 1.13)

  • selected - This is called when a user has made an item selected. The event_info parameter is the genlist item that was selected.

  • unselected - This is called when a user has made an item unselected. The event_info parameter is the genlist item that was unselected.

  • expanded - This is called when GenlistItem.expanded is called and the item is now meant to be expanded. The event_info parameter is the genlist item that was indicated to expand. It is the job of this callback to then fill in the child items.

  • contracted - This is called when GenlistItem.expanded is called and the item is now meant to be contracted. The event_info parameter is the genlist item that was indicated to contract. It is the job of this callback to then delete the child items.

  • expand,request - This is called when a user has indicated they want to expand a tree branch item. The callback should decide if the item can expand (has any children) and then call GenlistItem.expanded appropriately to set the state. The event_info parameter is the genlist item that was indicated to expand.

  • contract,request - This is called when a user has indicated they want to contract a tree branch item. The callback should decide if the item can contract (has any children) and then call GenlistItem.expanded appropriately to set the state. The event_info parameter is the genlist item that was indicated to contract.

  • realized - This is called when the item in the list is created as a real evas object. event_info parameter is the genlist item that was created.

  • unrealized - This is called just before an item is unrealized. After this call content objects provided will be deleted and the item object itself delete or be put into a floating cache.

  • drag,start,up - This is called when the item in the list has been dragged (not scrolled) up.

  • drag,start,down - This is called when the item in the list has been dragged (not scrolled) down.

  • drag,start,left - This is called when the item in the list has been dragged (not scrolled) left.

  • drag,start,right - This is called when the item in the list has been dragged (not scrolled) right.

  • drag,stop - This is called when the item in the list has stopped being dragged.

  • drag - This is called when the item in the list is being dragged.

  • longpressed - This is called when the item is pressed for a certain amount of time. By default it’s 1 second. The event_info parameter is the longpressed genlist item.

  • scroll,anim,start - This is called when scrolling animation has started.

  • scroll,anim,stop - This is called when scrolling animation has stopped.

  • scroll,drag,start - This is called when dragging the content has started.

  • scroll,drag,stop - This is called when dragging the content has stopped.

  • edge,top - This is called when the genlist is scrolled until the top edge.

  • edge,bottom - This is called when the genlist is scrolled until the bottom edge.

  • edge,left - This is called when the genlist is scrolled until the left edge.

  • edge,right - This is called when the genlist is scrolled until the right edge.

  • multi,swipe,left - This is called when the genlist is multi-touch swiped left.

  • multi,swipe,right - This is called when the genlist is multi-touch swiped right.

  • multi,swipe,up - This is called when the genlist is multi-touch swiped up.

  • multi,swipe,down - This is called when the genlist is multi-touch swiped down.

  • multi,pinch,out - This is called when the genlist is multi-touch pinched out.

  • multi,pinch,in - This is called when the genlist is multi-touch pinched in.

  • swipe - This is called when the genlist is swiped.

  • moved - This is called when a genlist item is moved in reorder mode.

  • moved,after - This is called when a genlist item is moved after another item in reorder mode. The event_info parameter is the reordered item. To get the relative previous item, use GenlistItem.prev. This signal is called along with “moved” signal.

  • moved,before - This is called when a genlist item is moved before another item in reorder mode. The event_info parameter is the reordered item. To get the relative previous item, use GenlistItem.next. This signal is called along with “moved” signal.

  • language,changed - This is called when the program’s language is changed.

  • tree,effect,finished - This is called when a genlist tree effect is finished.

  • highlighted - an item in the list is highlighted. This is called when the user presses an item or keyboard selection is done so the item is physically highlighted. The event_info parameter is the item that was highlighted.

  • unhighlighted - an item in the list is unhighlighted. This is called when the user releases an item or keyboard selection is moved so the item is physically unhighlighted. The event_info parameter is the item that was unhighlighted.

  • item,focused - When the genlist item has received focus. (since 1.10)

  • item,unfocused - When the genlist item has lost focus. (since 1.10)

  • changed - Genlist is now changed their items and properties and all calculation is finished. (since 1.16)

  • filter,done - Genlist filter operation is completed.. (since 1.17)

Enumerations

Genlist item types

efl.elementary.ELM_GENLIST_ITEM_NONE

Simple item

efl.elementary.ELM_GENLIST_ITEM_TREE

The item may be expanded and have child items

efl.elementary.ELM_GENLIST_ITEM_GROUP

An index item of a group of items

Genlist items’ field types

efl.elementary.ELM_GENLIST_ITEM_FIELD_ALL

Match all fields

efl.elementary.ELM_GENLIST_ITEM_FIELD_TEXT

Match text fields

efl.elementary.ELM_GENLIST_ITEM_FIELD_CONTENT

Match content fields

efl.elementary.ELM_GENLIST_ITEM_FIELD_STATE

Match state fields

Genlist items’ scroll-to types

efl.elementary.ELM_GENLIST_ITEM_SCROLLTO_NONE

No scroll to

efl.elementary.ELM_GENLIST_ITEM_SCROLLTO_IN

Scroll to the nearest viewport

efl.elementary.ELM_GENLIST_ITEM_SCROLLTO_TOP

Scroll to the top of viewport

efl.elementary.ELM_GENLIST_ITEM_SCROLLTO_MIDDLE

Scroll to the middle of viewport

efl.elementary.ELM_GENLIST_ITEM_SCROLLTO_BOTTTOM

Scroll to the bottom of viewport

Added in version 1.17.

Inheritance diagram